Wood has been used for many years as an important building and construction material and its importance as such is increasing for a number of reasons. Typical uses include general construction, residential housing, utility poles, cross arms, fence posts, railroad ties and pilings. Although wood is a renewable natural resource, it must be protected from attack by insects and fungus and marine organisms for many of these applications. Left unprotected or unpreserved such as by chemical treatment, wood will decay and deteriorate anywhere from within a few months to a few years, depending upon climate and soil conditions. Wood objects such as utility poles and timbers deteriorate rapidly below the ground and at ground level and would require frequent replacement if not properly and adequately preserved with a material which is both effective against attacking organisms and long lasting.
Through the years, a number of different materials have been used for preservation. Among these are included creosote, heavy metal salts, heavy oils and tars, pitch and various organic materials including chlorinated phenols, especially pentachlorophenol (PCP). Each of these materials has its advantages and disadvantages. Creosote, as well as other heavy oils and tars and pitch treatments, may have a strong odor and leave the surface greasy and oily to the touch.
Chlorinated phenols have found wide use because of their effectiveness, relative ease of application and durability. Because of its particularly good fungicidal and insecticidal properties, pentachlorophenol is widely used as a commercial wood preservative. It is normally dissolved in hydrocarborn solvents such as medium aromatic oils, volatile petroleum solvents (propane), light solvents (mineral spirits), or in a clorinated hydrocarbon solvent-inhibited grade of methylene chloride. Cosolvents are added in many instances to achieve proper solubility of pentachlorophenol in the solutions. Because energy conservation is becoming increasingly important, many of the traditional treating solvents are more valuable as feed stocks for other chemical products. Therefore, a low energy based solvent such as water has been sought as a replacement for these hydrocarbon solvents. The difficulty has been that pentachlorophenol in a simple admixture with water has little or no solubility. Prior art shows that pentachlorophenol can be reacted with sodium hydroxide in water to form the water soluble sodium pentachlorophenate. To date this is the only aqueous soluble form of pentachlorophenol that has been commonly used in the wood treating industry. However, sodium pentachlorophenate treating solution has a severe disadvantage in its excess leachability during field use and some lack in penetrating ability. In the practice of our invention, new water soluble pentachlorophenol, treating solutions are disclosed which overcome these problems even when using sodium pentachlorophenate.
The closest art known to the applicants is contained in the following U.S. Pat. Nos.: 1,919,298; 2,322,633, 2,908,607; 3,281,318; and 3,993,752.